Pivot to Spindle distance

Elliott, It is only a matter of rather simple geometry. Lewm has said everything else that needs to be said.

@markpao , don't bother Mark. As long as you have the right offset and overhang with the cartridge you are using you are in business. If the cantilever is parallel to both sets of lines then all of the above is true. The P2S distance is just to get you in the ballpark. You have already found your seat. Stay there. You just risk damaging something playing around.

Longer arms are not a panacea. They have a greater polar moment of inertia which causes much more distortion than any improvement in tracking error can resolve. This is why many of us prefer shorter arms and why many tonearm manufacturer's scratch their heads in response to this market demand. There are very few modern cartridges that require tonearms that heavy.